Primary dermal melanoma: A case report and molecular characterization

Primary dermal melanoma: a West Australian cohort

BACKGROUND

The objectives of this study were to identify a subgroup of patients with putative primary dermal melanoma after thorough multidisciplinary clinical and histological evaluation, and to describe the clinical, histological and selected molecular features of these lesions.

METHODS

The records of the Western Australian Melanoma Advisory Service were searched for potential cases of primary dermal melanoma. The clinical and histological features were reviewed, immunohistochemical assessment was performed and clinical outcomes recorded.

RESULTS

Eighteen cases of putative primary dermal melanoma with available clinical data were identified. Two of 12 cases in which further histological sections could be obtained were excluded because of the presence of findings suggesting an epidermal origin on these further sections. In one additional case, such origin could not be histologically excluded. Median follow-up period for the remaining cases was 68 months. Confirmed primary dermal melanoma accounts for 0.87% of cases of melanoma referred to a subspecialist melanoma advisory service. These cases show significant histological overlap with dermal/subcutaneous metastases of melanoma, but display a relatively good prognosis, with a 5-year survival of 87.5%.

CONCLUSION

Our results support the recognition of a distinct group of melanoma that mimics metastatic melanoma, but is associated with a relatively favourable outcome. The group of putative primary dermal melanoma is likely to be heterogenous, including cases of primary nodular melanoma in which epidermal connection has not been identified, metastatic melanoma with an occult primary lesion and true primary dermal melanoma.

Primary dermal melanoma in a patient with a history of multiple malignancies: a case report with molecular characterization

Introduction

Primary dermal melanoma (PDM) is a recently described clinical entity accounting for less than 1% of all melanomas. Histologically, it is located in the dermis or subcutaneous tissue, and it shows no connections with the overlying epidermis. The differential diagnosis is principally made along with that of metastatic cutaneous melanoma.

Case Report

A 72-year-old Caucasian woman with a history of multiple cancers (metachronous bilateral breast cancer, meningioma, clear cell renal cell carcinoma, uterine fibromatosis and intestinal adenomatous polyposis), came to our attention with a nodular lesion on her back. After removal of the lesion, the histology report indicated malignant PDM or metastatic malignant melanoma. The clinical and instrumental evaluation of the patient did not reveal any other primary tumour, suggesting the primitive nature of the lesion. The absence of an epithelial component argued for a histological diagnosis of PDM. Subsequently, the patient underwent a wide surgical excision with sentinel node biopsy, which was positive for metastatic melanoma. Finally, the mutational status was studied in the main genes that regulate proliferation, apoptosis and cellular senescence. No pathogenetic mutations in CDKN2A, BRAF, NRAS, KRAS, cKIT, TP53 and PTEN genes were observed. This suggests that alternative pathways and low-frequency alterations may be involved.

Conclusions

The differential diagnosis between PDM and isolated metastatic melanoma depends on the negativity of imaging studies and clinical findings for other primary lesions. This distinction is important because 5-year survival rates in such cases are higher than in metastatic cases (80–100 vs. 5–20%, respectively).

Primary dermal melanoma: a case report and a review of the literature

Patients with cutaneous metastatic melanoma of unknown primary origin (stage IV M1a disease according to the American Joint Committee on Cancer melanoma staging system) have an estimated 5-year survival rate of between 5% and 17.9% and a median survival of 6 months. However, certain patients with stage IV M1a disease have much higher survival rates. The existence of this subpopulation has given rise to the term primary dermal melanoma to describe such cases. We report a case of melanoma with characteristics consistent with primary dermal melanoma and review the relevant literature. A diagnosis of primary dermal melanoma requires careful clinical and pathologic correlation and should be considered in all patients with a solitary melanoma confined to the dermis and subcutaneous tissue when there is no evidence of a primary tumor or disease at other sites following appropriate staging studies. We believe that familiarity with this subtype of melanoma is essential in order to provide patients with optimal care and better prognostic information.

Spindle cell melanocytic lesions: part II—an approach to intradermal proliferations and horizontally oriented lesions

Melanocytic lesions show great morphological diversity in their architecture and the cytomorphological appearance of their composite cells. Whereas functional melanocytes show a dendritic cytomorphology and territorial isolation, lesional nevomelanocytes and melanoma cells typically show epithelioid, spindled or mixed cytomorphologies, and a range of architectural arrangements. Spindling is common to melanocytic lesions, and may either be a characteristic feature or a divergent appearance. The presence of spindle cells may mask the melanocytic nature of a lesion, and is often disconcerting, either due to its infrequent appearance in a particular lesion or its interpretation as a dedifferentiated phenotype. Spindle cell melanocytic lesions follow the full spectrum of potential biological outcomes, and difficulty may be experienced judging the nature of a lesion due to a lack of consistently reliable features to predict biological behaviour. Over time, recognition of numerous histomorphological features that may portend a more aggressive lesion have been identified; however, the translation of these features into a diagnostic entity requires a gestalt approach. Although most spindle cell melanocytic lesions may reliably be resolved through this standard approach, problem areas do exist for the surgical pathologist or dermatopathologist. With this review (part II of II), we complete our discussion of spindle cell melanocytic lesions, in order to: (1) model a systematic approach to such lesions; and (2) provide familiarity with those melanocytic lesions which either typically or occasionally display a spindled cytomorphology.