Clear cell melanoma of the skin with regressive changes

Clear Cell Melanoma: A Cutaneous Clear Cell Malignancy

Clear cell melanoma is a rare clear cell malignancy. Accurate diagnosis of clear cell melanoma requires integration of immunohistochemical and morphologic findings, with molecular studies to rule out clear cell sarcoma. The differential diagnosis includes melanoma, carcinoma, perivascular epithelioid cell tumor, and epidermotropic clear cell sarcoma. We use a case of a lesion on the helix of an 86-year-old man as an example. Histologic examination revealed an ulcerated clear cell malignant tumor. Tumor cell cytoplasm contained periodic acid-Schiff–positive, diastase-sensitive glycogen. Tumor cells showed positive labeling for S100, HMB-45, and Melan-A, and negative labeling for cytokeratins, p63, and smooth muscle actin. Molecular studies demonstrated BRAF V600E mutation, copy gains at the 6p25 (RREB1) and 11q13 (CCND1) loci, and absence of EWSR1-ATF1 fusion. These findings supported a diagnosis of clear cell melanoma. The rare pure clear cell morphology occurs due to accumulation of intracytoplasmic glycogen. We review the differential diagnosis of clear cell melanoma and describe the utility of immunohistochemical and molecular studies in confirming this diagnosis.

Clear cell variant of malignant melanoma of the uterine cervix: a case report and review of the literature

BACKGROUND

A rare variant of malignant melanoma of the uterine cervix mimicking clear cell carcinoma or clear cell sarcoma is described.

CASE

A 33-year-old Japanese woman was admitted to the hospital complaining of genital discharge and lower back pain. The stage was FIGO IIB and radical hysterectomy and pelvic lymphadenectomy were done. Pathological examination, immunohistochemical studies of melanin granules, and molecular analysis of the EWS/ATF-1 fusion gene were also done. A diffuse proliferation of amelanotic clear cells was detected in the uterine cervix. Tumor cells were positive for HMB 45, Melan-A (MART-1), and S-100 protein and negative for epithelial markers. The EWS/ATF-1 fusion gene was not detected.

CONCLUSION

This is apparently the first report of a case of clear cell melanoma of the uterine cervix. Despite its rarity, this variant of malignant melanoma should be considered when diagnosing clear cell neoplasms of the uterine cervix.

Morphological and immunophenotypic variations in malignant melanoma

A variety of cytomorphological features, architectural patterns and stromal changes may be observed in malignant melanomas. Hence, melanomas may mimic carcinomas, sarcomas, benign stromal tumours, lymphomas, plasmacytomas and germ cell tumours. Melanomas may be composed of large pleomorphic cells, small cells, spindle cells and may contain clear, signet-ring, pseudolipoblastic, rhabdoid, plasmacytoid or balloon cells. Various inclusions and phagocytosed material may be present in their cytoplasm. Nuclei may show bi- or multi-nucleation, lobation, inclusions, grooving and angulation. Architectural variations include fasciculation, whorling, nesting, trabeculation, pseudoglandular/pseudopapillary/pseudofollicular, pseudorosetting and angiocentric patterns. Myxoid or desmoplastic changes and very rarely pseudoangiosarcomatous change, granulomatous inflammation or osteoclastic giant cell response may be seen in the stroma. The stromal blood vessels may exhibit a haemangiopericytomatous pattern, proliferation of glomeruloid blood vessels and perivascular hyalinization. Occasionally, differentiation to nonmelanocytic structures (Schwannian, fibro-/myofibroblastic, osteocartilaginous, smooth muscle, rhabdomyoblastic, ganglionic and ganglioneuroblastic) may be observed. Typically melanomas are S100 protein, NKIC3, HMB-45, Melan-A and tyrosinase positive but some melanomas may exhibit an aberrant immunophenotype and may express cytokeratins, desmin, smooth muscle actin, KP1 (CD68), CEA, EMA and VS38. Very rarely, neurofilament protein and GFAP positivity may be seen.