Hypomelanotic Blue Nevi Lack Fingerprint CD34 Immunopositivity

*Department of Dermatology, Seth GS Medical College and KEM Hospital, Mumbai, India
The American Journal of dermatopathology (Impact Factor: 1.39). 01/2012; 34(3):342-3. DOI: 10.1097/DAD.0b013e31822c3ba8
Source: PubMed
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    ABSTRACT: Desmoplastic melanoma (DMM) is an uncommon melanoma variant with a distinct morphology, including a prominent spindle cell component with fibrosis, as well as a distinct immunohistochemical profile. Histologically, the spindle cell component of DMM can be confused with sclerotic/desmoplastic nevi, nonpigmented blue nevi, scar, and neural tumors. The histological distinction between sclerotic/desmoplastic/blue nevi and DMM using standard light microscopic techniques can be exceedingly subtle. Therefore, we investigated whether immunohistochemical staining for Melan-A and Ki-67 expression can be used to discriminate these lesions, distinguishing between epithelioid and spindle cell compartments of the lesions. Fifty cases of DMM and 13 cases of sclerotic/desmoplastic/blue nevi were identified. Standard immunohistochemical techniques were used with antibodies towards HMB-45, Melan-A (A103), and Ki-67; 43 of 50 DMM cases were available for staining with Melan-A, 42 of 50 for HMB-45, and 31 of 50 cases were stained with Ki-67. All 13 nevi were stained for Melan-A and 8 for Ki-67. Immunoreactivity to Ki-67 antibody was scored as 0 to 5%, 6 to 10%, 11 to 30%, or greater than 30% positive tumor cells. Only 3 of 43 and 3 of 42 of spindle cell compartments of DMMs were positive for Melan-A and HMB-45, respectively. Focal staining of epithelioid cells in the junctional component or superficial dermis was observed in 33% (14/43). In contrast, 100% of the 13 nevi were strongly positive for Melan-A (P < 0.001). Seventeen melanomas (55%) were 0 to 5% positive for Ki-67, five (16%) fell into the 6 to 10% category, three (10%) were between 11 and 30%, and six (19%) were at least focally greater than 30% positive. All 8 nevi (100%) had less than 5% positive cells for Ki-67 (P = 0.02), with only 2 cases having more than 2% positive cells. The sclerotic/desmoplastic and hypopigmented blue nevi were uniformly positive for Melan-A, while the vast majority of DMM were negative in their spindle cell compartments. Melan-A is very useful in distinguishing between DMM and sclerotic nevi. Ki-67 appears to be an inconsistent marker for DMM. However, a high labeling index (over 5%) may be used as a clue in diagnosing DMM.
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    ABSTRACT: Blue nevus and its variants typically present as pigmented lesions. Dermal melanin is responsible for coloration and is an expected histologic finding. Herein, we report 20 cases of an unusual amelanotic variant of cellular blue nevus. Our series showed clinical demographics similar to pigmented counterparts. Thus, there was a predilection for young individuals with a mean age of 24 years (range 6-74 years). Both sexes were affected, with a female-to-male ratio of approximately 2:1. The lower back, distal extremities, and scalp were the most common sites of occurrence. Importantly, the lack of pigmentation resulted in an atypical clinical appearance. A diagnosis of blue nevus by the attending physician was not considered in any of the reported lesions. All of the tumors extended deep into the reticular dermis or subcutaneous fat with a mean thickness of 5.5 mm (range 1.7-11 mm). Ulceration was present in two lesions. Mild cytologic atypia and pleomorphism were present in five cases. Mitotic activity (up to 3 mitoses/mm ) was observed in 11 lesions. A brisk lymphocytic host response was present in only one lesion. Tumor necrosis was not observed. Most, but not all, tumors showed reactivity for S-100 and HMB-45. Clinical follow-up (mean 32 months) was consistent with a benign course. Local recurrence was not observed after complete excision. None of the cases was associated with clinical evidence of lymph node or distant metastases. Recognition of amelanotic cellular blue nevus is important because the lack of expected pigmentation may result in clinical and pathologic diagnostic difficulty. In particular, amelanotic cellular blue nevus must be distinguished from malignant cellular blue nevus and other variants of melanoma.
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    ABSTRACT: Blue nevus is a benign pigmented lesion of dermal melanocytes with a number of histologic and clinical variants, of which the major types are the common blue nevus, cellular blue nevus and combined nevus. This study describes 9 cases of hypopigmented blue nevus (HBN), a variant of common blue nevus in which there is minimal identifiable melanin pigment. We also discuss the usefulness of the immunoperoxidase stain HMB-45 in relation to the diagnosis of HBN and the lesions with which it may be histologically confused, namely common intradermal nevus, dermatofibroma, neurofibroma, dermal scar and desmoplastic malignant melanoma. The HMB-45 stain was found to be uniformly positive in all 9 cases of HBN, in contrast to the other dermal lesions which have been reported as either negative or showing only focal positivity. The physical distribution and age range of the patients in this study was similar to the age and sites for common BN, supporting the relationship between the 2 lesions. The occurrence of HBN in predominantly young adults indicates that this lesion is not a phenomenon due to ageing or degenerative change, and should be regarded as a variant of common blue nevus.
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