Search for the SLNs

Compared with patients with cutaneous melanomas, those with anal or rectal melanomas (0.14.6% of all anal malignancies; 2-3% of all malignant melanomas) have a worse prognosis (Ben Iz-hak et al. 1997; Helmke et al. 2001).

The 5-year survival rate is less than 10%, which is the same as in cutaneous melanoma stage IV (Coit 1993).

The reason for this unfavorable biological behavior is not fully understood (unfavorable location? different genetically based tumor development and growth activity than in UV-induced cutaneous melanomas?) (Balch et al. 1979; Liw et al. 1996). Only one point seems to be clear: in contrast to malignant melanomas located higher in the rectal mucosa, melanomas of the anal circle may invade hemorrhoidal veins early and metasta-size directly into the lungs via the azygos veins.

In patients with rectal melanomas, in the search for SLNs the same principles can be applied as in the case of rectal cancer (see Chapter 26, pp. 391393). On the basis of new developments, peritu-moral 99mTc-labeling and the search for retrorectal lymph nodes using the gamma probe seems to be a method that would reward further development.

In melanomas of the anal circle (see Fig. 8), as well as rectal amputation the search for retrorectal lymph nodes (followed by en bloc resection) is obligatory in cancer clearance. In addition, it is necessary to search for inguinal and/or para-iliacal lymph nodes as possible sentinel nodes. Individual surgical treatment along these guidelines is the method of choice (Weinstock 1993; Whooley et al. 1997).

So far there are no data on benefits of adjuvant chemotherapy (Vorpahl et al. 1996). In conclusion, no scheme has yet been developed that would make it possible to find a single SLN or node groups in the different possible basins.

Immunohistochemical Support in the Diagnosis of Dysplastic Nevi and Early Invasive Malignant Melanomas

For the diagnosis of dysplastic nevi and very early intraepidermal melanoma development, as well as early stromal invasion, immunohistochemical double staining, for instance using antibodies directed to S100 protein and proliferative nuclear antigen (Ki 67, MiBI), is very helpful.

Double staining of S100 protein and Ki 67 (MiBI) active against the proliferation acthive protein helps to exclude increased proliferation, and with this malignancy, on the one hand (Fig. 9), or to confirm increased proliferation of S100-positive nevus cells that are already atypical on the other (Fig. 10). In addition, early stromal invasion can be detected by these immunohistochemical staining procedures.

Possibilities for Cytopathological Confirmation of the Diagnosis of Malignant Melanomas in Cancer-infiltrated Lymph Nodes in Cases with Primarily Undetected Primaries

In cases in which no locoregionally located malignant melanoma or other primary has been detected, suspicious, mostly enlarged, lymph nodes can be aspirated by way of a fine needle and the smears can

Fig. 9. Dermal nevus cell nevus. The in-traepithelial and the dermal nevus cell populations are intensively stained with the antibody directed to S100 protein. Only a few nuclei are stained with MiBI, almost exclusively basal cells of the epidermis

Fig. 10. Small sector of a dysplastic nevus cell nevus. Besides basal cells, in some higher cell layers a few nevus cells (S100 protein, positive with brown-stained granules) are also MiBI positive. Some intraepithelial nuclei show apop-totic changes

Fig. 11 a-d. Diagnosis of occult malignant melanomas in fine-needle aspiration cytology (FNAC) from lymph nodes (Giemsa and immunohistochem-ical stainings). a FNAC of an amelano-tic malignant melanoma with partly epithelial layered cell populations; no pigment can be detected. Note round nuclei, some with central prominent nucleoli. b Amelanotic malignant melanoma, same tumor, stained with the melanoma-specific antibody HMB45. c Malignant melanoma cell populations with strongly positive reaction using antibodies directed to the mesenchymal cell marker vimentin (intermediary filament). Note: All malignant melanomas are vimentin positive

Fig. 11 d. Malignant melanoma cell populations stained with antibodies directed to cytokeratins. Note: Newer results show that a small percentage of malignant melanomas show coexpression for cytokeratins. The cytokeratin positivity can result in a pitfall with the diagnosis of carcinoma

be analyzed by Giemsa staining and immunohisto-chemically. Some characteristic stainings, illustrated in Fig. 11 a-d, document the characteristic antigenic features of malignant melanomas.

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