๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Locally invasive cellular blue nevus
Locally invasive cellular blue nevus
Superficial atypical melanocytic proliferations of unknown significance
Superficial atypical melanocytic proliferations of unknown significance (SAMPUS) is a proposed designation for lesions that are difficult to separate from melanoma in situ or minimally invasive melanoma in the radial growth phase.1,2 Defined as such, lesions designated as SAMUPS have limited, if any, capability for giving rise to metastatic disease since they lack a tumorigenic growth phase. Lesions designated as SAMPUS are generally cured by local excision with safe margins of 3โ5โฏmm.1
Clinical features This very rarely documented variant of cellular blue nevus presents in the scalp as a deeply infiltrating tumor which may involve the skull, meninges, and brain with resultant neurological abnormalities.1,2 In the two cases described in the literature, one patient was alive and free from neurological abnormalities 13 months after surgery.1 In another, widespread metastatic melanoma developed 3 years after incomplete surgery.2 No further follow-up was recorded.
Histologic features Extensive involvement of the skull, dura, and brain is characteristic of this tumor. Although no overt histologic features of frank malignancy were identified in either of the two cases documented, the very deeply infiltrating growth pattern combined with evidence of metastatic disease in one case suggests that this entity would be better regarded as a malignant rather than a locally aggressive variant of cellular blue nevus.
Histologic features The epidermal melanocytic component consists of a focal continuous lentiginous proliferation of melanocytes with random mild to moderate cytological atypia and limited upward migration of isolated melanocytes or individual nests.1 Importantly, however, these changes are focal in nature and do not extend across the entire lesion. There is no severe cytological atypia. Furthermore, uniform nuclear atypia and mitoses are generally lacking. In the dermis, a few atypical melanocytes without mitotic activity can be observed.2
In the background, the histologic features of a junctional or compound dysplastic nevus, pigmented spindle cell nevus of Reed, or Spitz nevus are sometimes seen.
Comment It seems unlikely that this represents a truly homogenous entity and that examination of additional sections and deeper levels will allow a more
1304 Melanocytic nevi
precise categorization in the overwhelming majority of cases. In such difficult cases, the opinion of experts in the field should also be sought. We do not recommend use of this diagnostic category. It has the inherent danger of becoming a wastepaper basket diagnosis for any difficult melanocytic lesion that does not appear to readily fit into a specific category. It most certainly is of little use to the clinician or the patient!