Positivity For Smooth Muscle Actin Research Articles

Pulmonary “inflammatory myofibroblastic” tumors: a critical examination of the diagnostic category based on quantitative immunohistochemical analysis

The World Health Organization classification applies the term "pulmonary inflammatory myofibroblastic tumor" to a histologically variegate set of pulmonary inflammatory pseudotumors. However, often these lesions bear little resemblance to tumors of myofibroblastic origin. To elucidate histogenesis, we examined 18 cases from our institution files. The cases were stained with antibodies to smooth muscle actin (SMA), Factor XIIIa, CD3, CD20, CD68, S-100, anaplastic lymphoma kinase (ALK-1), and human herpevirus-8 (HHV-8). The percentage of positive-staining cells within a defined tumor area (400,000 microm(2)) was determined by light microscopy and morphometric analysis. Ten cases (56%) showed myofibroblastic differentiation, as judged by positive SMA staining of spindle cells. All cases showed substantial numbers of CD68+, Factor XIIIa+, and S-100+ monocytoid cells. Fifty percent were ALK-1+, and one was HHV-8+. We conclude that the term "inflammatory myofibroblastic tumor" is a misnomer, as nearly half of cases show no myofibroblastic differentiation. Instead, the results suggest that these lesions are composed predominantly of cells of macrophage-dendritic cell lineage. Although the multiplicity of terms previously applied to these lesions is cumbersome, retaining a descriptive phenomenological terminology may ultimately promote accurate elucidation of pathogenesis.

Symplastic hemangioma: report of two cases

Symplastic hemangioma is characterized by degenerative atypia of vascular smooth muscle and interstitial cells within a pre-existing vascular lesion with minimal endothelial cell atypia. We describe an additional two cases of this distinctive but poorly recognized entity. On histology, both lesions revealed a cirsoid aneurysm-type appearance with thick-walled and variably dilated blood vessels. The vascular endothelial cells showed mild nuclear hyperchromasia with no multilayering or mitoses. The atypical cells, either located within the vascular smooth muscle wall or within the interstitium, were spindle or epithelioid with varying degrees of hyperchromasia, nuclear enlargement, pleomorphism, and multinucleation. Perivascular hemorrhage, vascular thrombosis, and focal papillary endothelial hyperplasia were uniformly present. The variably fibrous to edematous stroma showed hemosiderin deposits and a mononuclear inflammatory infiltrate. Clusters of adipocytes were present within the superficial dermis. Rare atypical mitoses and occasional bizarre lipoblast-like stromal cells were identified in one tumor. Immunohistochemistry showed focal smooth muscle actin positivity in the pleomorphic cells of the vascular walls. CD68 and CD34 stained occasional stromal cells in the interstitial location. Both the cases showed no recurrence. The bizarre cytologic changes are interpreted as degenerative in nature and probably akin to that observed in ancient schwannoma and uterine symplastic leiomyoma.

Severe Feto-Placental Abnormalities Precede the Onset of Hypertension and Proteinuria in a Mouse Model of Preeclampsia1

Preeclampsia is a prevalent and potentially devastating disorder of pregnancy. Characterized by a sudden spike in blood pressure and urinary protein levels, it is associated with significant obstetric complications. BPH/5 is an inbred mouse model of preeclampsia with borderline hypertension before pregnancy. BPH/5 mice develop hypertension, proteinuria, and endothelial dysfunction during late gestation (after E14.5). We hypothesized that BPH/5 mice might exhibit early feto-placental abnormalities before the onset of maternal disease. All placental cell lineages were present in BPH/5 mice. However, the fetal and placental weights were reduced, with abnormalities in all the placental zones observed starting early in gestation (E9.5-E12.5). The fractional area occupied by the junctional zone was significantly reduced at all gestational timepoints. Markedly fewer CDKN1C-stained trophoblasts were seen invading the proximal decidual zone, and this was accompanied by reductions in Cdkn1c gene expression. Trophoblast giant cell morphology and cytokeratin staining were not altered, although the mRNA levels of several giant cell-specific markers were significantly downregulated. The labyrinth layer displayed decreased branching morphogenesis of endothelial cells, with electron microscopy evidence of attenuated trophoblast layers. The maternal decidual arteries showed increased wall-to-lumen ratios with persistence of actin-positive smooth muscle cells. These changes translated into dramatically increased vascular resistance in the uterine arteries, as measured by pulse-wave Doppler. Collectively, these results support the hypothesis that defects at the maternal-fetal interface are primary causal events in preeclampsia, and further suggest the BPH/5 model is important for investigations of the underlying pathogenic mechanisms in preeclampsia.

ALK expression in pseudosarcomatous myofibroblastic proliferations of the genitourinary tract

Pseudosarcomatous myofibroblastic proliferation of the genitourinary tract is rare and may develop after trauma or spontaneously. The aim of this study was to characterize further the clinicopathological features of these lesions and to examine their relationship to inflammatory myofibroblastic tumour (IMT). Twenty-seven cases of pseudosarcomatous myofibroblastic proliferation were analysed. There were seven males and 20 females; median age was 37 years (range 16-88). Most lesions were from the bladder (n = 21), while others were in the urethra, vulva, vagina, rectum and retrovesical space. Median tumour size was 30 mm (range 6-120 mm). Seven cases (25%) had a history of prior trauma or surgery. Three cases recurred locally but not destructively. The tumours had fasciitis-like features including bland spindle cells with evenly distributed chromatin, admixed inflammatory cells (mainly lymphocytes) and often a myxoid stroma. Immunohistochemistry showed positivity for smooth muscle actin in 14/20 cases, keratin in 8/19, desmin in 7/20 and anaplastic lymphoma kinase (ALK) in 10/21 cases. Fluorescent in situ hybridization was performed in six ALK+ cases; all were negative for ALK gene rearrangement. Pseudosarcomatous myofibroblastic proliferations of the genitourinary tract may show ALK immunopositivity but do not show consistent ALK rearrangement. Given subtle morphological differences and more consistently benign behaviour, their relationship to inflammatory myofibroblastic tumour at other sites remains uncertain.

Plexiform lipoleiomyoma of the uterus: first case report

We describe the first report of plexiform lipoleiomyoma with amyloid stroma. A 57-year-old woman underwent an abdominal hysterectomy for methrorragia. The hysterectomy specimen exhibited a soft, rubbery, encapsulated 11 cm ovoid mass with aciniform, white cut surface on the right edge of the uterus. The histology was distinctive and typical of plexiform lipoleiomyoma: long cords, strands and small nests of cells embedded in a collagenous matrix. The neoplastic cells showed eosinophilic cytoplasm, crumpled, bland nuclei. Scattered islands of mature adipocytes were distributed throughout the leiomyomatous proliferation. Immunohistochemistry showed positivity for smooth muscle actin in the plexiform component, and for S100 in the adipocytes. Histogenesis and origin of the cellular neoplastic component are discussed.

Perivascular myoma of myopericytoma and myofibromatosis‐type arising in a chronic scar

We describe a case of a cutaneous perivascular myoma with features overlapping between the myofibromatosis and the myopericytoma type. The patient is a 58-year-old woman with a painless plaque-like and multinodular lesion in the pretibial dermis and subcutaneous tissue. She had repeated trauma to this site, first in her early youth that left an area of hyperpigmentation, and then again at age 40. The biopsy showed a biphasic pattern with a myofibromatosis-type component composed of spindle cell myoid nodules and more cellular round cell areas. The myopericytoma-like areas appeared to be infiltrating along vessels. These areas contained aggregates of immature-appearing cells arranged concentrically around vascular lumina in a manner reminiscent of pericytes. Immunohistochemical stains showed focal positivity for smooth muscle actin. Immunohistochemical and ultrastructural studies have showed these pericyte-like cells to be of a myoid origin. The reason for the neoplastic proliferation of perivascular myoid cells is presently unknown. The association of trauma and neoplastic transformation of the skin is rare. We report the first case of a cutaneous perivascular myoma arising in a chronic scar.

Malignant Glomus Tumor of the Urinary Bladder

We present a case of a malignant glomus tumor arising in the urinary bladder of a 57-year-old woman with metastatic pulmonary nodules who died 2 months later. Pathologically and clinically confirmed malignant glomus tumors are exceedingly rare, especially those that arise in the visceral organs. The present case retained its architectural similarity to a benign glomus tumor and consisted of sheets of highly malignant round cells showing cytoplasmic positivity for smooth muscle actin. On reticulin histochemical staining, we found that reticulum fibrils surrounded individual tumor cells, suggesting cellular investment by basement membrane. We discuss the concept of malignant glomus tumors and emphasize the criteria that distinguish them from other malignant tumors.

Malignant glomus tumor of the urinary bladder.

We present a case of a malignant glomus tumor arising in the urinary bladder of a 57-year-old woman with metastatic pulmonary nodules who died 2 months later. Pathologically and clinically confirmed malignant glomus tumors are exceedingly rare, especially those that arise in the visceral organs. The present case retained its architectural similarity to a benign glomus tumor and consisted of sheets of highly malignant round cells showing cytoplasmic positivity for smooth muscle actin. On reticulin histochemical staining, we found that reticulum fibrils surrounded individual tumor cells, suggesting cellular investment by basement membrane. We discuss the concept of malignant glomus tumors and emphasize the criteria that distinguish them from other malignant tumors.

Deficient innervation characterizes intestinal strictures in a rat model of colitis

Intestinal strictures are a common complication of Crohn's disease leading to serious consequences. With unknown etiology and cellular composition, strictures can be neither prevented nor reversed by current therapeutic strategies, and research has been limited by the lack of a well-developed animal model. We observed the sporadic occurrence of intestinal strictures at Day 35 in the TNBS rat model of colitis, which persisted beyond Day 90. Strictured tissue showed fusion, thickening, and disorganization of the smooth muscle layers. Immunocytochemistry revealed that all strictures were characterized by deficient innervation with a complete loss of intrinsic neurons, and a 92% loss of total axons per area. The number of α-smooth muscle actin-positive smooth muscle cells (SMC) increased in strictures, but immunolabeling showed phenotypic modulation of these cells, with the SMC phenotype (desmin-positive, vimentin-negative) entirely replaced by a myofibroblast phenotype (desmin-negative, vimentin-positive). Although cellular structure still predominated in the strictured regions, histochemistry showed increased extracellular matrix collagen, from 6 ± 0.9% to 22 ± 4% of total area. With previous evidence for neural loss in colitis, and in vitro studies showing neural regulation of smooth muscle cell (SMC) growth, we conclude that the regional loss of innervation may initiate tissue re-modeling that is characteristic of stricture formation.

Immunohistochemical Differentiation and Clinicopathological Features of Canine Gastrointestinal Stromal Tumors and Leiomyosarcomas

Introduction: Gastrointestinal stromal tumors (GIST) and leiomyosarcomas (LMS) have recently been differentiated by immunohistochemical staining techniques and have been shown to have different biological behaviors in humans. Expression of the c‐kit protein, a transmembrane tyrosine kinase receptor, occurs in nearly all GISTs. The aim of this study was to differentiate canine GIST from LMS, and to compare their clinicopathological features.Methods: Archived blocks of previously diagnosed LMS were analyzed. Immunohistochemical staining using antibodies against c‐kit, smooth muscle actin (SMA), desmin, vimentin and S100 was performed. GISTs were diagnosed based on positive c‐kit staining. LMS were diagnosed based on absence of c‐kit staining and positive SMA staining. Follow‐up information was obtained from medical records and telephone interviews with owners.Results: Forty‐two dogs were included in the study. Mean age was 10.9 yrs (range 5–15 yrs). There were 18 females and 24 males. Twenty‐eight tumors were GISTs, 10 were LMS and 4 stained negatively for c‐kit, SMA and S100 (sarcomas). GISTs were more likely to occur in the large intestine and LMS were more common in the small intestine (p = 0.01). All were surgically excised and only two were treated with adjunctive chemotherapy. Only two GISTs and one sarcoma had metastasized at the time of surgery. Survival time in dogs discharged after surgery for GIST, LMS and sarcomas was 1123, 233 and 88 days respectively (p = 0.08).Conclusions: Many previously diagnosed LMS should be reclassified as GIST based on the results of immunohistochemical staining. The biological behavior of these tumors appears to be different.

Primary leiomyoma of the ovary co‐existing with serous cystadenofibroma

A 48-year-old woman with a 14 cm left ovarian mass had total abdominal hysterectomy and bilateral salpingo-oophorectomy. On cut section the tumor had a solid and a cystic component. There was a 2.5 cm nodule attached to the cyst wall. Sections taken from the solid component revealed a tumor composed of interlacing bundles of fusiform cells, resembling a leiomyoma. Smooth muscle actin positivity confirmed the diagnosis. Sections taken from the nodule in the cystic part revealed an adenofibroma. There was an SMA positive area in the cyst wall which we think is the possible origin of the leiomyoma. As far as we know, this is the first case of a co-existing leiomyoma and serous cystadenofibroma in the ovary, and we think it will broaden the histological spectrum of primary ovarian leiomyomas.

Multifocal Infantile Fibromatosis

Infantile fibromatosis (IF) is an uncommon childhood disorder characterized by solitary or muticentric tumors involving skeletal muscle, skin, bones, or viscera. There is a wide morphologic spectrum reflecting various stages of fibroblastic differentiation. We present the clinical and histopathologic findings of a rare case of IF. A seven month old female presented with firm masses over the right elbow (2 × 3 cm.) and right distal clavicle (3 × 4 cm.). Magnetic resonance imaging demonstrated increased T2 signal within the soft tissues of the right axilla, supraclavicular region, and distal humerus. However, there was no evidence for bony involvement. Incisional biopsy of the supraclavicular mass showed a white fibrous grossly appearing tumor. Histologic examination revealed clusters of adipocytes and infiltration of skeletal muscle fibers by a moderately cellular proliferation of ovoid within a fibrous background. There was no atypia, necrosis, or increased mitotic activity. The tumor cells showed diffuse immunoreactivity for vimentin and weak focal positivity for smooth muscle actin. No reactivity was seen with S100. In addition, none of the tumor cells exhibited nuclear estrogen receptor expression by image cytometry. This case is reported in an effort to better define the clinical and histopathologic features of infantile fibromatosis.

Perivascular Myoma of Myofibromatosis and Myopericytoma‐Type Arising in a Chronic Scar: A Case Report

We describe a case of a cutaneous perivascular myoma with features overlapping between the myofibromatosis and the myopericytoma type. The patient is a 58‐year‐old female with a painless plaque‐like and multinodular lesion in the pretibial dermis. She reported repeated trauma to this site, first in her early youth that left an area of hyperpigmentation, and then again at age 40. She had noticed the appearance of nodules in this area 5 years prior to presentation, which had increased in size and number over the last six months. The biopsy showed a biphasic pattern with a myofibromatosis type component composed of spindle cell myoid nodules and more cellular round cell areas. The myopericytoma‐like areas appeared to be infiltrating along vessels. These areas contained aggregates of immature cells arranged concentrically around vascular lumina reminiscent of pericytes. Immunohistochemical stains showed focal positivity for smooth muscle actin. Immunohistochemical and ultrastructural studies have shown these pericyte‐like cells to be of a myoid origin. The reason for the neoplastic proliferation of perivascular myoid cells is presently unknown. The association of trauma and neoplastic transformation of the skin is rare. We report the first case of a cutaneous perivascular myoma arising in a chronic scar.

Aggressive angiomyxoma of the female genital tract: a clinicopathologic and immunohistochemical study of 12 cases

Aggressive angiomyxoma (AAM) is a distinctive neoplasm seen in the female genital tract. We present the clinicopathological findings of 12 female patients with AAM. Immunohistochemical analysis for vimentin, desmin, smooth-muscle actin (SMA), muscle-specific actin (MSA), S-100, CD44, estrogen receptor (ER), and progesterone receptor (PR) was performed. Mean patient age was 39 years (range 20–77 years). Eight tumors arose in the vulva, two in the suburethral area, and two in the perirectal area. Three were pedunculated (two vulvar and one suburethral). Perineal tumors were locally excised, with limited removal of adjacent tissue or tissue surrounding the pedicle base of pedunculated tumors. Perirectal tumors were removed by wide excision. Tumors ranged 2.8–40.0 cm in size. Eleven patients were followed-up (mean 19 months). Recurrence occurred in one patient 48 months after tumor resection from perirectum and abdomen. Immunohistochemistry showed tumor positivity for vimentin (11/11), desmin (8/11), CD44 (8/11), ER (10/12), PR (11/12), and SMA (3/11). MSA and S-100 were negative. In summary, AAM in the perineum especially pedunculated tumors may possibly require only local excision for definitive treatment. Furthermore, the majority of AAM have CD44 expression.

Aggressive angiomyxoma of the female genital tract: a clinicopathologic and immunohistochemical study of 12 cases

Aggressive angiomyxoma (AAM) is a distinctive neoplasm seen in the female genital tract. We present the clinicopathological findings of 12 female patients with AAM. Immunohistochemical analysis for vimentin, desmin, smooth-muscle actin (SMA), muscle-specific actin (MSA), S-100, CD44, estrogen receptor (ER), and progesterone receptor (PR) was performed. Mean patient age was 39 years (range 20-77 years). Eight tumors arose in the vulva, two in the suburethral area, and two in the perirectal area. Three were pedunculated (two vulvar and one suburethral). Perineal tumors were locally excised, with limited removal of adjacent tissue or tissue surrounding the pedicle base of pedunculated tumors. Perirectal tumors were removed by wide excision. Tumors ranged 2.8-40.0 cm in size. Eleven patients were followed-up (mean 19 months). Recurrence occurred in one patient 48 months after tumor resection from perirectum and abdomen. Immunohistochemistry showed tumor positivity for vimentin (11/11), desmin (8/11), CD44 (8/11), ER (10/12), PR (11/12), and SMA (3/11). MSA and S-100 were negative. In summary, AAM in the perineum especially pedunculated tumors may possibly require only local excision for definitive treatment. Furthermore, the majority of AAM have CD44 expression.

Plaque‐Like Myofibroblastic Tumor of Infancy

We report two unrelated infants that presented for evaluation of large dermal plaques that histologically resembled dermatofibromas. The clinical appearance and histochemical staining, however, support a myofibroblastic origin of the neoplasms. The patients were a 13 month old female with a slowly growing, pink, firm, irregular plaque that was first noticed at 3 months of age, and an 11 month old boy who presented with a pruritic, slowly growing, irregular, nodular plaque that was noticed shortly after birth. MRI revealed no extension of tumor into deeper subcutaneous tissues in either infant. Both infants had normal growth and development. Biopsies of both infants’ plaques revealed spindle cell neoplasms dissecting through collagen bundles throughout the entire dermis with overlying psoriasiform epidermal hyplerplasia. The spindle cells were predominantly haphazardly arranged but in a few areas were arranged in small fascicles. Both tumors stained positively for Factor XIIIa and were focally smooth muscle actin positive. Staining for CD34 was negative in both neoplasms. Histologically, both tumors resembled dermatofibromas; however the clinical appearance and positive smooth muscle actin staining best fit with a myofibroblastic neoplasm. The features of this neoplasm and the differential of other spindle cell tumors of infancy will be reviewed.

Rosuvastatin exerts favourable effects on thrombosis and neointimal growth in a mouse model of endothelial injury

Apart from reducing systemic lipid levels, statins may improve the clinical course of atherosclerosis by exerting favourable pleiotropic effects on the vessel wall. We studied the effects of rosuvastatin, a new, potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on vascular remodelling after endothelial injury in the hyperlipidaemic apolipoprotein E-knockout (apoE-/-) mouse. ApoE-/- mice, 22-weeks-old, were injected daily with rosuvastatin at a low (1 mg/kg; n=27) or high dosage (10 mg/kg; n=24), or with vehicle alone (n=26). After treatment for 2 weeks, endothelial injury and thrombosis of the carotid artery was induced with 10% ferric chloride. Treatment was then resumed for a 3-week period. Although statin treatment did not affect the plasma lipid levels of mice, mean times to arterial thrombosis were prolonged in the low-dose and the high-dose group compared to controls (P<0.05 and P<0.01 respectively). Interestingly, rosuvastatin withdrawal 4 days before injury completely reversed the antithrombotic effects of the drug. In follow-up studies 3 weeks after injury, deposition of fibrin in the vessel wall was significantly reduced in the rosuvastatin-treated animals. There was an increase in the content of alpha-actin-positive smooth muscle cells (P=0.008) and collagen fibers (P<0.001), and a concomitant decrease in the number of oxLDL-containing macrophages (P<0.001). Overall, the neointimal area and the severity of luminal stenosis were significantly reduced in statin-treated mice. Thus, rosuvastatin attenuates arterial thrombosis and neointima formation, and it may stabilise vascular lesions developing after endothelial injury in mice. These effects are independent of systemic lipid lowering.

Ductal carcinoma in situ with spindle cells: a potential diagnostic pitfall in the evaluation of breast lesions.

To evaluate the morphological features of 11 cases of breast ductal carcinoma in situ (DCIS) with spindle cells and to propose an approach to distinguish it from benign mimics. The association with neuroendocrine differentiation was also investigated. Cases of breast DCIS with a spindle cell component diagnosed in the Department of Pathology, Singapore General Hospital, between June 1996 and January 2003, were included in the study. The histological characteristics were documented, and immunohistochemistry for neuroendocrine markers, hormone receptors, cerbB2, smooth muscle actin (SMA) and high-molecular-weight (HMW) cytokeratins, was carried out. Electron microscopy was carried out on reprocessed paraffin-embedded material in three cases. Of 11 women diagnosed with DCIS with spindle cells, four presented with nipple discharge, six with a breast lump, while one was discovered to have a screen detected density. The tumour size ranged from 3 to 41 mm. The proportion of spindle cells varied from 10% to 80% of the in-situ tumour cell population. Nuclear grade was low in seven cases and intermediate in four. Necrosis was observed in two cases. Architectural pattern was papillary in six cases, and mixed in the rest. Microinvasion was present in two cases, with possible microinvasion in another two. Immunohistochemistry for neuroendocrine markers synaptophysin and chromogranin showed positive reactivity for at least one marker in all but three cases; one of these latter cases demonstrated ultrastructural neurosecretory granules. Oestrogen and progesterone receptors were expressed in 10 and nine cases, respectively, while cerbB2 was positive in only one case. HMW cytokeratin immunoprofile revealed a general lack of immunostaining within the abnormal cell population; likewise, no positivity for SMA of the cellular proliferation was detected. Almost all DCIS lesions with spindle cells disclose neuroendocrine differentiation. Although the distinction from benign florid usual hyperplasia may pose a diagnostic histological problem, the presence of diffuse neuroendocrine expression, in conjunction with the pattern of HMW keratin profile on immunohistochemistry, supports an in-situ neoplastic process. The absence of SMA immunostaining, in conjunction with negative reactivity for cytokeratins 5/6 and 14, makes the possibility of a myoepithelial proliferation unlikely.

Anaplastic lymphoma kinase (ALK 1) staining and molecular analysis in inflammatory myofibroblastic tumours of the bladder: a preliminary clinicopathological study of nine cases and review of the literature

Inflammatory myofibroblastic tumours (IMFT) may arise at any anatomical site, including lung, soft tissues, retroperitoneum and bladder. Although morphologically similar, these lesions encompass a spectrum of entities with differing aetiology, ranging from reactive/regenerative proliferations to low-grade neoplasms with a risk of local recurrence, but no significant metastatic potential. Vesical IMFT usually presents as a polypoid mass with a pale firm cut surface and can be of considerable size, mimicking a malignant tumour clinically and radiologically. Its good outcome, however, warrants conservative surgical excision, emphasising the importance of identification and distinction from malignant tumours of the bladder that may require more radical surgery and/or adjuvant therapy. We conducted a preliminary retrospective, comparative immunocytochemical study of 20 bladder tumours, including nine IMFTs, five spindle cell (sarcomatoid) carcinomas, two rhabdomyosarcomas, two leiomyosarcomas and two neurofibromas. The results confirmed IMFT positivity for smooth muscle actin, desmin and cytokeratin in 78–89% cases, resulting in potential confusion with sarcomatoid carcinoma or leiomyosarcoma. In contrast, cytoplasmic anaplastic lymphoma kinase (ALK 1) staining was present in eight IMFT (89%), but was not seen in any other lesion examined. The ALK 1 staining was confirmed by fluorescence in situ hybridisation, with translocation of the ALK gene present in 15–60% tumour cells in four of six IMFT examined, but not in four cases of sarcomatoid carcinoma or three of leiomyosarcoma. In conclusion, ALK 1 staining may be of value in the distinction of vesical IMFT from morphologically similar entities, and often reflects ALK gene translocations in these lesions.

Desmoplastic melanoma of the head and neck: histopathologic and immunohistochemical study of 28 cases.

Studies of the immunohistochemical profiles and clinical course of desmoplastic melanoma have produced conflicting results. We identified 28 cases of desmoplastic melanoma after a search of our files for spindle cell neoplasms of the head and neck from 1960 through 1995. The 17 male (61%) and 11 female (39%) patients averaged 65 years of age. The cheek was the most common location (12 cases, 43%). The average length of follow-up was 5 years. Overall 5-year survival rate was 46%. Melan A and tyrosinase positivity (P = 0.0195), smooth muscle actin positivity (P = 0.0328), tumor size (P = 0.0297), and tumor thickness (P = 0.0419) were significantly associated with local progression-free survival. No histologic or immunohistochemical marker was associated with overall or metastasis-free survival.