Large primary cutaneous melanomas convey an ominous risk of metastases. The finding of large-scale melanomas without regional or distant metastases suggests a less aggressive biology for this type of tumor.
A man in his 60s presented with a 2-year history of a bleeding mass on his left thigh. Examination revealed a 6.0 × 8.2-cm fungating tumor with a 4-mm palpable left inguinal node. The patient underwent wide excision with clear margins. Histologic examination of the excision revealed an expansile proliferation of epithelioid neoplastic cells with abundant cytoplasm and prominent nucleoli. The tumor extended into the subcutaneous tissue to a depth of 6 cm. The tumor cells were positive for Mart-1 and S-100 immunostains. An in situ component and ulceration were identified. Five mitoses/mm2 were identified, and there was no evidence of lymphovascular invasion. Fine-needle aspiration biopsy of the enlarged lymph node identified no malignant cells. One sentinel lymph node in the left inguinal region was negative for metastasis, and whole-body positron emission tomography (PET)/computed tomography (CT) scan showed no evidence for metastatic disease. He declined chemotherapy and was disease free at last follow-up, 4 years after diagnosis.
A man in his 60s presented with a 1-year history of an 8 × 7-cm tumor on his left back associated with fever and left axillary lymphadenopathy (Figure). Histologic sections of the surgical resection revealed a nodular proliferation of atypical and epithelioid melanocytes that extended into the reticular dermis to a depth of 2.4 cm. Sixteen mitoses/mm2 were identified, and the margins were negative. Two sentinel lymph nodes in the left axilla were negative for metastasis by S-100 and Mart-1 immunostains. A chest, abdomen, and pelvis CT scan and subsequent whole-body PET scan were negative for metastatic disease. The patient died 4 months after diagnosis due to chronic cardiac disease.
An 8 × 7-cm erythematous eroded mass was noted on the back of patient 2.
Cases of giant primary melanoma, defined as lesions at least 10 cm in diameter1 or 48 mm in thickness,2 are almost exclusively associated with extensive metastatic disease.1 To our knowledge, only 2 other cases of giant primary melanoma without extensive metastasis have been described in the literature.3,4
Studies have illustrated that certain primary melanoma subtypes are associated with favorable prognostic outcomes. Desmoplastic melanoma is a rare variant with variable presentation that is marked histologically by fusiform melanocytes in a sclerotic stroma.5 Investigators have found that patients with pure desmoplastic melanoma (desmoplasia found throughout the tumor) have a more advanced Breslow depth and less regional metastasis than patients with conventional melanoma.5 Primary dermal melanoma, a more recently described variant that is confined to the dermis and may histologically resemble cutaneous metastasis, also appears to have improved survival compared with metastatic melanoma or primary nodular melanoma of equal Breslow thickness.6
These cases challenge the current belief that large primary cutaneous melanoma of long duration connotes extensive metastatic disease and/or rapid death. Although our conclusions are somewhat limited by the inability to assess long-term outcomes in patient 2, both patients reported a prolonged duration of symptoms and had negative findings on metastatic workup, suggesting a less aggressive biology for these tumors. With the discovery of various genetic mutations in primary melanomas, there has been a recent movement to reclassify melanoma subtypes based on genetic profile, which may predict pathologic behavior and therefore outcome more accurately than histopathologic features. We propose that these cases may represent a distinct genetic subtype of giant melanoma that, while locally aggressive, lacks propensity for metastasis.
Corresponding Author: Daniela Kroshinsky, MD, MPH, Harvard Medical School, Massachusetts General Hospital, 50 Staniford St, Ste 200, Boston, MA 02114 (firstname.lastname@example.org).
Published Online: January 29, 2014. doi:10.1001/jamadermatol.2013.6892.
Conflict of Interest Disclosures: None reported.
Additional Contributions: We are indebted to Greg Sakamoto, MD, for his help with the diagnosis and management of these interesting cases.
Chong TA, Strazzula L, Hoang MP, Arakaki R, Kroshinsky D. Giant Primary Melanoma With No Apparent Metastases: A Report of 2 Cases. JAMA Dermatol. 2014;150(5):574-575. doi:10.1001/jamadermatol.2013.6892