Intraepidermal Component Research Articles

Presentation and Management of Porocarcinoma: A Systematic Review with Meta-Analysis of More Than One Thousand Patients

Introduction Porocarcinoma is an aggressive cutaneous carcinoma arising from the intraepidermal component of the sweat glands. Given its uncommon nature, only a limited number of studies have addressed this issue. This study summarizes the different presentations and management of the disease. Methods The eligible databases were searched to identify English-language studies published up to January 16th, 2024. The inclusion criteria comprised studies that focused on the presentation and management of eccrine porocarcinoma, with a clear statement of the outcomes of the chosen management. The data collected from the studies included the first author's name, country of study, type of study design, patient demography, the clinical presentation of the tumor and its location, histopathological findings, metastasis status, treatment strategy, and the subsequent prognosis. Results The initial search yielded 817 papers, with only 22 meeting the inclusion criteria. The studies comprised 1004 patients with a mean age of 78.7 years. In total, 527 (52.5%) of them were male and 461(45.9%) were female. The most commonly affected regions were the head and neck followed by the lower extremities. The most frequent treatment option was surgical excision in 876 (87.3%) patients. Distant metastasis accounted for about 2%, while lymph node involvement, occurred in 36 cases (3.6%). A good prognosis was reported in 57.3% of the cases. Both the age and tumor size had a significant effect on prognosis (p <0.05). ConclusionThe lesion can develop anywhere on the body, with a survival rate exceeding 50%. Wide-based surgical excision remains the predominant treatment option.

MITF::CREM-rearranged tumor: a novel group of cutaneous tumors with melanocytic differentiation.

Cutaneous tumors with melanocytic differentiation represent a broad group of neoplasms of both melanocytic and non-melanocytic origin. Besides traditional members such as clear-cell sarcoma (CCS) and PEComa, the latter group has recently expanded to also include MITF::CREM fusion-associated tumors, but the available data are limited. Herein, we present a third case of this rare neoplasm which occurred in the temporal region in a 1-year-old girl. It was an infiltratively growing polypoid dermal-based lesion lacking an intraepidermal component. It consisted of cellular solid sheets or small nests of epithelioid to spindled cells with a predominantly eosinophilic and much less commonly clear cytoplasm. The nuclei had round to ovoid shape and exhibited moderate to high-grade atypia and prominent nucleoli. The mitotic activity was 11 mitoses per 10 high-power fields, and atypical mitotic figures were present. Immunohistochemically, the tumor was strongly positive with S100 protein, SOX10, and MITF, while HMB45, tyrosinase, and Melan A were negative. Extensive molecular analysis revealed only MITF::CREM gene fusion. There had no evidence of disease 9 months after the diagnosis. These tumors need to be distinguished from malignant tumors with melanocytic differentiation, primarily from melanoma. However, additional cases still need to be studied to precisely define their biological potential and establish their nosologic status.

Compound Clear Cell Sarcoma of the Skin-A Potential Diagnostic Pitfall: Report of a Series of 4 New Cases and a Review of the Literature.

The proliferation of cells with melanocytic lineage and a nested pattern has traditionally been regarded as a characteristic feature of a wide range of benign and malignant melanocytic proliferations. Herein, we report a series of 4 clear cell sarcomas, including 3 primary cutaneous and 1 metastatic to the skin, associated with a clear-cut intraepidermal proliferation of tumor cells representing a serious potential diagnostic pitfall. All patients were male individuals, aged from 17 to 71 years (mean: 42 y). The size of the tumors ranged from 8 to 55 mm (mean: 22.2 mm, median: 13 mm). Two tumors arose on a lower extremity and 1 each on the scalp and chest. Cutaneous metastasis developed on the limb proximal to the amputation site. Histologically, all tumors were variably circumscribed nodular or multinodular proliferations within the dermis, focally extending into the subcutis. They were composed of nests and fascicles of pale spindled and epithelioid cells with finely granular or pale cytoplasm, elongated nuclei with a single prominent nucleolus, featuring mild nuclear pleomorphism, and surrounded by delicate fibrous septa. Scattered wreath-like giant cells were present in all cases. Mitotic activity was low (mean and median: 3.5 mitoses/mm). The intraepidermal component consisted in all 4 cases of nests of tumor cells localized at the dermal-epidermal junction. Nests were well-defined and composed of spindled or epithelioid cells with irregular hyperchromatic nuclei, prominent nucleoli, and scant to moderately abundant eosinophilic to pale cytoplasm. Lentiginous proliferation of epithelioid tumor cells was coupled with focal upward migration of isolated tumor cells in a single case. By immunohistochemistry, all tumors were S100 protein, melan A, and HMB45 positive. By fluorescence in situ hybridization analysis, 3 tumors displayed rearrangements in the EWSR1 gene, whereas reverse transcriptase polymerase chain reaction confirmed EWSR1(e8)/ATF1(e4) translocation in the remaining case. In conclusion, an epidermal component in primary cutaneous clear cell sarcomas, or cutaneous metastasis of the tumor, is exceptional and represents a potential diagnostic pitfall. Careful attention to the salient morphologic features in the dermal component of the tumor, as well as confirmation of EWSR1 gene rearrangement by fluorescence in situ hybridization or reverse transcriptase polymerase chain reaction, is necessary for correct recognition of the tumor and to avoid erroneous diagnosis of a benign or malignant melanocytic proliferation.

Desmoplastic melanoma: a challenge for the oncologist.

To evaluate clinical, pathologic and genetic features of desmoplastic melanoma (DM). Analysis of all DM records from 1991 to 2015. The most common location of DMs was the head and neck (69%); median age and follow-up were 60.5 and 7.3 years, respectively. A familial predisposition for DMs and others malignancies was analyzed. Thin Breslow thickness (<4.5 mm) was associated with an intraepidermal component or a previous lentigo maligna, whereas high Breslow thickness (>4.5 mm) was observed in 'pure' DM. DM could progress from an early phase, characterized by an intraepidermal component, to late phase, characterized by a dermal nodule. This hypothesis correlates with melanoma genetic and NF1 mutation, which could be an early event in the progression of DM.

Subcutaneous Malignant Melanoma developing in Congenital Giant Naevus with Complete Spontaneous Regression of Superficial Dermo-Epidermal Part:A Case Report

Giant congenital melanocytic nevi a ≥ 20 cm is rare in adolescents and adults. Here we present a case of subcutaneous melanoma developing in congenital giant naevus with complete regression of superficial dermoepidermal part. A 17 yr old girl presented with a painless and gradually increasing swelling in her right temporal region on pre-existing giant congenital menocytic naevus (GCMN) on right hemiface. FNAC proved the case as malignant melanoma of temporal region with metastatic deposit in cervical lymph node. On histopathological examination it was found that the melanoma arising deep in the subcutaneous tissue with extensive involvement of deeper structures, extensive metastasis of cervical lymph nodes, salivary glands, deeper soft tissues with spontaneous regression of superficial epidermal and dermal part. Though regression is seen in melanomas, spontaneous regression has been mostly seen in melanomas with only intraepidermal component.

Nodular malignant melanoma. Or maybe not?

On histopathological examination, there was a wellcircumscribed epithelial proliferation of monomorphic cuboidal cells, with focal evidence of ductal differentiation (Fig. 2). In the lateral intraepidermal component, the proliferation was composed of similar cells with heavily pigmented cytoplasm, forming nests that were fairly well-demarcated from the adjacent keratinocytes (Fig. 3). Rare mitoses were seen, but there were no atypical mitotic figures or cytological atypia.

Neurofibroma-Like Spindle Cell Melanoma

We present a case that highlights the use of two maneuvers useful in the diagnosis of spindle cell melanoma. A shave biopsy from the cheek of a 58-year-old man demonstrated a thin invasive melanoma of 0.3 mm thickness with a less than 2-mm-wide intra-epidermal component. Below this melanocytic lesion, but not contiguous with it, there was a transected S-100-positive and Melan-A-negative spindle cell proliferation. Upon re-excision, no residuum of conventional melanoma was identified, but a residual spindle cell neoplasm that was 4 mm in diameter, nodular, well-circumscribed, cytologically bland, and S-100 positive was noted. At our consensus conference, our group favored neurofibroma but agreed that spindle cell melanoma could not be excluded based on histopathologic features alone. To further address the differential diagnosis, we performed CD34 staining that demonstrated lack of a CD34 fingerprint. We also completed array-based comparative genomic hybridization, which demonstrated gain of chromosome 6p, loss of 6p and gain of 7. These two methods of analysis support a diagnosis of spindle cell melanoma.

Unusual variants of cutaneous melanoma

Melanomas possess a remarkable capacity for morphological diversity and even divergent differentiation. Classification of these unusual variants is based on the recognition of a specific growth pattern (e.g. pseudoglandular, angiomatoid) or a unique cytological attribute (e.g. clear cell, balloon cell, rhabdoid). Unusual morphology may be encountered in primary, metastatic or recurrent tumours alike. Some variants are so named because of their ability to mimic benign melanocytic proliferations (e.g. naevoid, Spitzoid). Most are not associated with specific prognostic differences. Instead, their importance resides in the potential for confusion with a wide range of benign and malignant neoplasms. Diagnosis of melanoma is less problematic when lesions are pigmented and/or if there is an intra-epidermal component. Purely dermal neoplasms, however, pose a diagnostic challenge, especially when amelanotic. Immunohistochemistry is often invaluable in confirming the diagnosis of melanoma and excluding the histopathological differential diagnosis associated with several unique variants discussed in this review.

Intraepidermal and dermal Merkel cell carcinoma with squamous cell carcinoma in situ: a case report with review of literature

Merkel cell carcinoma (MCC), a rare aggressive primary cutaneous neuroendocrine carcinoma, occurs on sun-damaged skin, especially in the elderly. Its unique co-expression of cytokeratin 20 (CK20) and neuroendocrine markers, including neuron-specific enolase (NSE), is diagnostic. Most MCCs are located in the dermis, rarely has an intraepidermal component been reported. We report a case of MCC with an intraepidermal component admixed with squamous cell carcinoma in situ (SCCIS). We were able to identify the differences in the immunohistochemical expression pattern between that of the intraepidermal and the dermal components. Most intraepidermal neoplastic cells of MCC in this case showed a less intense immunoreactivity to CK20 and NSE compared to that of dermal neoplastic cells. This case reports an unusual occurrence of combined SCC and MCC that shows both intraepidermal and dermal components.

Desmoplastic Malignant Melanoma: A Clinicopathologic Analysis of 113 Cases

Desmoplastic melanoma (DM) is a rare variant of spindle cell melanoma, which usually develops in sun-damaged skin of elderly patients. Often the lesion is nonpigmented and frequently mistaken for a nonmelanocytic proliferation, which delays diagnosis and treatment and therefore worsens the prognosis. The spindle shape of neoplastic melanocytes, the prominent desmoplasia, and the frequent neurotropism of neoplastic melanocytes are its most characteristic histopathological features. We have studied the clinicopathologic features of 113 cases of DM. The mean age of the patients was 71.1 years; 48% of the patients were males and 52% were females. The neoplasm was located on the head in 72% of the cases. Malignant melanoma was the initial clinical diagnosis in only 27% of the cases. Histopathologically, all lesions appeared as poorly demarcated neoplasms that involved the entire dermis and often extended into the subcutaneous tissue. The neoplasms were composed of ill-defined fascicles of spindle cells. Desmoplasia was defined as the presence of spindle cells associated with a fibrotic stroma. Fifty-one cases (45%) were classified as "pure DM" when the lesion was entirely desmoplastic, and 62 cases (55%) were considered as "combined DM" when a recognizable desmoplastic component was seen in an otherwise conventional malignant melanoma. In 81% of the cases, an atypical intraepidermal melanocytic component (in situ malignant melanoma) was identified, whereas in the remaining 19% of the cases the intraepidermal component was lacking. Seventy-one percent of the cases were histologically amelanotic, 23% showed a small amount of pigment, and only 6% were heavily pigmented. Neural involvement was identified in 40/113 cases (35%), predominantly in the thickest tumors. Lymphoid nodules, found in 42/113 cases (37%), were significantly more frequent in pure DM than in combined DM (53% vs 24%). The null hypothesis of homogeneity of the "pure" and "combined" subgroups should be rejected (P < 0.002). Solar elastosis, with variable intensity, was seen in 82% of the cases. Mean Breslow thickness was 4.1 mm (4.6/3.7 mm, in the pure/combined subgroups, respectively), median was 4.0 mm (4.0/3.0 mm); Breslow thickness ranged from 0.3 to 11.0 mm, with half of the cases thicker than 4 mm. Only 4% of the cases showed Clark level below IV. The predominant neoplastic cells consisted of spindle-shaped melanocytes in 85% of the cases, whereas the remaining 15% of the cases demonstrated round neoplastic cells forming the main mass of the neoplasm. The mitotic rate of the neoplastic cells was low in 72% of the cases, 23% had an intermediate mitotic rate, and 5% showed a high mitotic rate. On follow-up, 55/113 patients (49%) (with an average of 55 months) demonstrated persistence of the disease. About 4% had local recurrences, 2% of lymph node invasion, 9% systemic metastases, and 12% died from the disease (2 cases of pure DM and 5 cases of combined DM). Although a better prognosis has been postulated for DM when compared with conventional cutaneous malignant melanomas of the same thickness, in most cases, a DM is diagnosed only in established long-standing and thick melanomas. Therefore, dermatologists and dermatopathologists should be more aware of this clinicopathologic variant of cutaneous malignant melanoma.

Acral lentiginous melanoma: histopathological prognostic features of 121 cases

Acral lentiginous melanoma (ALM) is the fourth histopathological subtype of malignant melanoma, accounting for < 10% of all melanomas in white-skinned populations. It is characterized by a lentiginous pattern of proliferation of the intraepidermal component of the tumour. Its individualization is still controversial, especially in regard of its prognostic value. To characterize better ALM from a pathological point of view and to assess the prognostic value of all histopathological features of ALM. We performed a review of all cases of ALM followed from 1996 to 2004 at the University Hospital Department of Dermatology, Lyon, France. We examined all haematoxylin, eosin and saffron-stained tissue sections of the primary lesions. Several pathological parameters of interest in melanoma were evaluated for disease-free and specific survival with the Kaplan-Meier method and the Cox proportional hazards regression model. Representative histological material was available for 121 patients. The mean Breslow thickness was 2.5 mm (in situ-20 mm). Fifteen lesions (12%) were in situ, nine (7%) were at Clark level II, 35 (29%) at III, 40 (33%) IV and 22 (18%) V. Extension along adnexal structures was found in almost half of the ALMs (46%), without prognostic significance. Seventeen (14%) lesions showed no microscopic pigmentation. Remnants of pre-existing naevus were found in four (3%) melanomas. The width of the 36 (30%) ulcerated lesions ranged from 1 to 20 mm (mean 7.6). Ulceration and its width were both associated with a large tumour thickness (P < 0.01), a high level of invasion (P < 0.01), the presence of vascular invasion (P < 0.01) and the lack of pigment production (P < 0.01). Among the 99 ALMs which were in the vertical growth phase (VGP), 21 showed a high mitotic rate (> 6 mitoses mm(-2)). A high mitotic rate was found to be significantly associated with the presence of ulceration (P < 0.01). The presence of microscopic satellites was noted in 10 (10%) lesions. The uncommon presence of small cells (8%) in the VGP was statistically significantly (P < 0.01) associated with a worse prognosis compared with other cell types. Multivariate analysis identified mitotic rate (P < 0.01), microsatellites (P = 0.05), Clark level (P = 0.01) and gender (P = 0.03) as independent prognostic factors for disease-free survival. Only the presence of microsatellites (P = 0.02) and a high mitotic rate (P < 0.01) were independently correlated with specific survival in ALM. This is a detailed pathological study of a large cohort with ALM, an uncommon subtype of melanoma. Mitotic activity appears to be of particular importance in predicting the outcome of ALM.

Primary cutaneous neuroendocrine cell carcinoma (Merkel cell carcinoma) with prominent microcystic features, mimicking eccrine carcinoma

Although primary cutaneous neuroendocrine cell carcinoma [Merkel cell carcinoma (MCC)] may show divergent features, including microcystic ('tubuloglandular'), squamous, eccrine and rhabdomyoblastic, a diffuse microcystic pattern is exceedingly rare. In this study, we present two cases of MCC with prominent microcystic features, which precluded a definitive diagnosis in the initial punch biopsy. Both patients were middle-aged men with a history of rapidly growing plaques of the back or posterior neck. Punch biopsies from both patients revealed an infiltrating neoplasm with prominent microcystic features that mimick tubuloglandular structures, lined by hyperchromatic basaloid cells, which were strongly positive for chromogranin and BerEP4, variably positive for CK7 and CK5/6 and negative for CK20, synaptophysin, S-100, epithelial membrane antigen (EMA), gross cystic disease fluid protein-15 (GCDFP-15), estrogen/progesterone receptors (ER/PR), thyroid transcription factor 1 (TTF1) and carcinoembryonic antigen (CEA). The re-excision specimens showed a multifocal intra-epidermal component in one case and typical finely stippled nuclear chromatin in both cases. Although the lack of CK20 staining is unusual, the histologic characteristics along with the remaining immunohistochemical studies favor the diagnosis of a primary cutaneous neuroendocrine cell carcinoma over the variants of eccrine carcinoma or basal cell carcinoma with neuroendocrine differentiation. Our cases illustrate that prominent microcystic features, mimicking glandular differentiation, may occur in MCC and pose a diagnostic challenge in small biopsy specimens.

Primary Melanoma of the Skin and Cutaneous Melanomatous Metastases

Through careful clinicopathologic correlation, we identified 37 metastatic melanomas in the skin, all of which had intraepidermal components. These were compared with 43 microscopically similar primary melanomas with a predetermined panel of immunostains in general use in surgical pathology, including bcl-2 protein, mutant p53 protein, Ki-67 (MIB-1), proliferating cell nuclear antigen (PCNA), alpha-isoform actin, and CD117 (c-kit protein). There was no significant difference in bcl-2 or alpha-isoform actin staining patterns of primary vs secondary cutaneous melanomas. The expression of Ki-67 generally was higher in metastatic melanomas than in primary lesions, and the same was true of mutant p53 protein labeling; however, some overlap was observed. CD117 staining was retained in 65% of metastatic melanomas (24/37) when they originated from ocular primary tumors; nevertheless, that marker was lost in virtually all of the other metastatic melanocytic neoplasms, whereas primary melanomas demonstrated consistent reactivity for c-kit protein. Although they are not definitive, these trends in immunoreactivity could facilitate the process of distinguishing the multiple primary melanoma syndrome from melanomatous metastases to the skin. That undertaking is best approached with circumspection, because clinicopathologic discriminators for this diagnostic separation are still imperfect.

Primary Melanoma of the Skin and Cutaneous Melanomatous Metastases : Comparative Histologic Features and Immunophenotypes

Through careful clinicopathologic correlation, we identified 37 metastatic melanomas in the skin, all of which had intraepidermal components. These were compared with 43 microscopically similar primary melanomas with a predetermined panel of immunostains in general use in surgical pathology, including bcl-2 protein, mutant p53 protein, Ki-67 (MIB-1), proliferating cell nuclear antigen (PCNA), α-isoform actin, and CD117 (c-kit protein). There was no significant difference in bcl-2 or α-isoform actin staining patterns of primary vs secondary cutaneous melanomas. The expression of Ki-67 generally was higher in metastatic melanomas than in primary lesions, and the same was true of mutant p53 protein labeling; however, some overlap was observed. CD117 staining was retained in 65% of metastatic melanomas (24/37) when they originated from ocular primary tumors; nevertheless, that marker was lost in virtually all of the other metastatic melanocytic neoplasms, whereas primary melanomas demonstrated consistent reactivity for c-kit protein. Although they are not definitive, these trends in immunoreactivity could facilitate the process of distinguishing the multiple primary melanoma syndrome from melanomatous metastases to the skin. That undertaking is best approached with circumspection, because clinicopathologic discriminators for this diagnostic separation are still imperfect.

Overexpression of p53 is correlated with stromal invasion in extramammary Paget’s disease of the vulva

Molecular alterations that are associated with clinicopathological features of extramammary Paget’s disease of the vulva (PDV) are poorly understood. Consequently, we have investigated whether a correlation exists between overexpression of p53 protein and various clinicopathologic features of PDV. Our study group comprises 10 primary noninvasive PDVs, 3 primary PDVs with minimal invasion, and 1 primary PDV with frank invasion. Recurrence in the form of noninvasive PDV was seen in 4 patients with previously noninvasive PDVs and in 1 patient who previously had PDV with minimal invasion. Metastases to the inguinal lymph nodes were associated with the 1 PDV with frank invasion and 1 of the PDVs with minimal invasion. An immunohistochemical study of p53 expression was performed on paraffin-embedded tissue. Negative p53 immunostaining was seen in all of the primary noninvasive PDVs as well as their recurrences. Positive p53 immunostaining was observed in the invasive as well as the intraepidermal components of all of the primary PDVs with invasion, the metastatic tumors in the inguinal lymph nodes, and the recurrent PDV associated with prior invasion, indicating a possible role of p53 in the progression of PDV. To our knowledge, our observation of p53 overexpression in the intraepidermal component of PDVs associated with invasion is the first to be reported in the literature. This observation may prove helpful in identifying stromal invasion in small biopsies. We also report for the first time an association between high nuclear grade in PDV and the propensity for inguinal lymph node metastasis.

Interphase cytogenetic analysis of 1q12 satellite III DNA in melanocytic lesions: increased aneuploidy with malignant histology.

To examine the relationship of chromosome 1 copy number to melanocytic tumorigenesis, interphase cytogenetic analysis of 1q12 satellite III DNA was performed on the spectrum of melanocytic lesions comprising Clark's tumor progression model. Results showed increased copy number in a "step off" pattern between melanoma in-situ and the intraepidermal component of invasive melanoma rather than a progression between each lesional group. These findings support Clark's concept of independent clonal expansion of a cell population giving rise to the vertical growth phase and further demonstrates increased chromosome 1 copy number as a late event in melanoma tumor progression.

Carcinomas of Sweat Glands Report of 60 Cases

c Context.—Several aspects of sweat gland carcinomas (incidence, classification, diagnosis, and behavior) have not been definitively clarified and need to be studied further. Objective.—The clinicopathologic findings of a large series of sweat gland carcinomas, collected during a period of 15 years, are presented. Methods.—Sixty sweat gland carcinomas (41 porocarcinomas, 3 syringomatous carcinomas, 8 ductal carcinomas, 5 adenoid cystic carcinomas, and 3 mucinous carcinomas) were analyzed histologically and immunohistochemically. Results.—Porocarcinomas were composed of eosinophilic and clear atypical cells arranged in solid-cystic lobular masses. These tumors were divided into 2 subgroups: horizontal porocarcinomas, showing a prominent intraepidermal component, and nodular porocarcinomas, which demonstrated predominant nodular growth. Syringomatous carcinomas presented keratinizing and nonkeratinizing cysts, dilated tubules (sometimes with a ‘‘tadpole’’ appearance), small neoplastic ducts, solid islands, and cellular cords. Ductal carcinomas were characterized by a prominent formation of tubules, solid islands, and cellular cords. Adenoid cystic carcinomas presented a characteristic pattern, showing basaloid monomorphous cells with moderately atypical nuclei, arranged in cribriform or solid islands and in tubular structures. Mucinous carcinomas were composed of moderately atypical cells with eosinophilic vacuolated cytoplasm, forming solid and cystic islands floating in large mucin pools. Immunohistochemically, cytokeratin was found in neoplastic cells in all cases, carcinoembryonic antigen was detected in 73% of cases, and actin-positive (myoepithelial) cells were not found. Conclusions.—Although numerous studies have been published in recent years, the histologic features, histogenesis, and classification of sweat gland carcinomas still remain controversial and need to be clarified by further studies. (Arch Pathol Lab Med. 2001;125:498‐505)

Carcinomas of sweat glands: report of 60 cases.

Several aspects of sweat gland carcinomas (incidence, classification, diagnosis, and behavior) have not been definitively clarified and need to be studied further. The clinicopathologic findings of a large series of sweat gland carcinomas, collected during a period of 15 years, are presented. Sixty sweat gland carcinomas (41 porocarcinomas, 3 syringomatous carcinomas, 8 ductal carcinomas, 5 adenoid cystic carcinomas, and 3 mucinous carcinomas) were analyzed histologically and immunohistochemically. Porocarcinomas were composed of eosinophilic and clear atypical cells arranged in solid-cystic lobular masses. These tumors were divided into 2 subgroups: horizontal porocarcinomas, showing a prominent intraepidermal component, and nodular porocarcinomas, which demonstrated predominant nodular growth. Syringomatous carcinomas presented keratinizing and nonkeratinizing cysts, dilated tubules (sometimes with a "tadpole" appearance), small neoplastic ducts, solid islands, and cellular cords. Ductal carcinomas were characterized by a prominent formation of tubules, solid islands, and cellular cords. Adenoid cystic carcinomas presented a characteristic pattern, showing basaloid monomorphous cells with moderately atypical nuclei, arranged in cribriform or solid islands and in tubular structures. Mucinous carcinomas were composed of moderately atypical cells with eosinophilic vacuolated cytoplasm, forming solid and cystic islands floating in large mucin pools. Immunohistochemically, cytokeratin was found in neoplastic cells in all cases, carcinoembryonic antigen was detected in 73% of cases, and actin-positive (myoepithelial) cells were not found. Although numerous studies have been published in recent years, the histologic features, histogenesis, and classification of sweat gland carcinomas still remain controversial and need to be clarified by further studies.

Small cell malignant melanoma: a variant of naevoid melanoma. Clinicopathological features and histological differential diagnosis

Aims—To describe the clinical and histopathological features of a rare variant of naevoid melanoma, small cell melanoma, and discuss the histological differential diagnoses. Methods—The clinical and histological features of cases...

Progression to invasive melanoma frommalignant melanoma in situ, lentigo maligna type

We have previously hypothesized that lesions that have been termed lentigo maligna can be divided into 2 categories: 1 represents a pigmented lesion that is a precursor to melanoma, and the other melanoma in situ. We and others have hypothesized that there is a progressive acquisition of attributes in pigmented lesions that results in malignant melanoma. Based on these 2 hypotheses, we have predicted that the intraepidermal component of invasive malignant melanomas, lentigo maligna type, should be similar to those lesions that we have termed malignant melanoma in situ, lentigo maligna type rather than lentigo maligna. The intraepidermal component of 42 consecutive cases of invasive malignant melanoma, lentigo maligna type was evaluated by all of the authors. Malignant melanoma in situ, lentigo maligna type is characterized by pagetoid spread, confluence, and nesting of atypical melanocytes. All of the cases evaluated showed features diagnostic of malignant melanoma in situ, lentigo maligna type, in the epidermis overlying the invasive dermal component. We conclude that invasive lentigo maligna melanoma arises in association with those lesions that we have termed malignant melanoma in situ, lentigo maligna type, which may represent a step in the progression between atypical melanocytic hyperplasia (lentigo maligna) and invasive melanoma. This fording supports the distinction of these entities and may have therapeutic implications.