Kamino bodies.

Abstract

Hideko Kamino [Figure 1], a world-renowned American dermatopathologist, among her boundless medical contributions, is credited for describing pinkish, round globules with irregular edges, located above the papillary dermis known as Kamino bodies (KBs, also known as eosinophilic globules) in 1979.[1] KBs were originally described in Spitz nevi; however, there are reports of its presence in other lesions, such as Reed nevus, “spitzoid” tumor and malignant melanoma (MM).[2]Figure 1: Dr. Hideko Kamino, world-renowned American dermatopathologistKBs histopathologically are solitary rounded or confluent, amorphous, eosinophilic masses of basement membrane material, found at the dermo-epidermal junction, most commonly at the tips of dermal papillae [Figures 2 and 3], in some Spitz nevi and far less commonly, in other benign and malignant melanocytic proliferations. KBs are hyaline structures that stain positively with periodic acid-Schiff and trichrome and are commonly found in the dermo-epidermal junction [Figure 4]. The eosinophilic nature of these structures is often obscured by melanin pigmentation.[3]Figure 2: Pointed arrow Kamino bodies (H&E)Figure 3: Illustrated Kamino bodiesFigure 4: Kamino bodies (PAS, ×200 and ×1.000)KBs were once believed to have been degenerated basal cells or melanocytes. However, studies have shown that they comprise collagen (type IV and VII), laminin and fibronectin, among other substances. In 1979, Kamino et al. described dull pink globules in the epidermis of 65% of junctional, 75% of the compound and 25% of intradermal types of Spitz nevi (the nevi of large spindle and/or epithelioid cells). These globules were periodic acid–Schiff (PAS)-positive, diastase resistant and positive on trichrome staining. Similar eosinophilic globules were noted in the epidermis in only 2% of malignant melanomas and 0.9% of ordinary melanocytic nevi. The globules in malignant melanomas and ordinary melanocytic nevi were negative with PAS and trichrome staining. Kamino et al. concluded that PAS and trichrome-positive eosinophilic globules in the epidermis can aid in the histological differentiation of Spitz nevus from malignant melanoma.[1234] Clusters of KBs are so much more common in Spitz nevi than in other lesions that they form an important diagnostic clue. However, their presence does not rule out melanoma completely because a rare melanoma contains similar clustered KBs. In H&E sections, KBs show some resemblance to Civatte bodies, as can be found in lichen planus or colloid bodies or a number of eosinophilic hyaline globules [Table 1] in the dermo-epidermal junction, so the following distinguishing features helps one identify true KBs.[1234567]Table 1: Distinguishing features between kamino bodies and colloid bodiesSubsequently, recent research has confirmed the presence of KBs in melanomas, among them Ackerman et al., who considered them to be rare in melanomas, Arbuckle and Weedon, who spotted them in 12% of melanomas, and Peters and Goellner, who claimed to have recognized them in 26% of melanomas. No author, however, even those who thought they had seen KBs in more than a quarter of melanomas, has ever stated that those bodies could be numerous in melanomas.[4] LeBoit reported that with the globules of most dermatopathologists thus “KBs can be large and numerous in Spitz nevus. Although they can occur on rare occasions in melanomas, they are often small and few.”[5] Moreover, in one quote from Arbuckle, one image shown as KBs may have actually been a dyskeratotic cell in the dermo-epidermal junction. Hence, the presence of KBs in MM is uncertain, but they appear to be rare or absent.[67] In sum, there is an inclination among many pathologists, worldwide, to equate many dull pink globules within the epidermis of a melanocytic neoplasm with Spitz nevus. That assumption can lead to serious errors in diagnosis because KBs may be numerous in melanomas. We conclude that KB, pigmented or nonpigmented, is a common histological finding in Spitz nevus and can be a good marker to aid in their differentiation from MM. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest. Acknowledgments Dr. Mohan K. P. Professor, Department of Oral and Maxillofacial Pathology and Microbiology, College of Dental Sciences, Davengere, Karnataka.