Melanoma cells in a lymphatic sinus
Malignant melanocytes, immunohistochemically positive for S100 protein, in a sentinel lymph node
(da C. Urso, L. Borgognoni, L. Vaggelli, A. Giannini, A. Salvadori, E. Zini, U.M. Reali: Linfonodo sentinella nel melanoma cutaneo: l'esperienza nell'area fiorentina. Pathologica 95: 133-139,2003)
Micrometastasis of melanoma in a sentinel lymph node
A sentinel lymph node is the first lymph node which drain a cutaneous region in a lymphatic basin. It seems to be the most probable site of early metastases from melanoma. In melanoma patients, a sentinel lymph node negative indicates that all other lymph nodes of a lymphatic basin are negative. On the contrary, the presence of a metastasis in a sentinel lymph node requires that a selective lymph node dissection is performed. Starting from the studies of Morton (1992), the technique of sentinel lymph node has spread in the world and also in Italy; in Florence, it has been adopted in our Hospital in June 1997. In these years (June 1997-December 2001), 322 patients have been treated.
The sentinel lymph node is identified using a vital blue dye, which may be associated with a radiocooloid injected in the area of the primary tumor. The first lymph node which assumes the blue dye or radiocolloid is considered the sentinel lymph node of that area. It is isolated, excised and sent to the histopathology laboratory. In laboratory, it is cut in two halves and frozen at -25°C; then several 6-microns sections (from 6 to 8) are stained with ematoxylin and eosin and examined at microscope. The procedure requires about 15 minutes. If the exam is positive, the surgeon performs a lymphadenectomy at once. Subsequently, the entire lymph node is cut in slices 2 mm thick and embedded in paraffin. From each paraffin block, 10 sections are cut to be stained with ematoxylin and eosin and 2 other sections to be immunohistochemically studied (S100 protein and HMB45).
Of the 322 patients studied, 182 were female and 140 male. The mean age was 55.2 years (range 18-88). The sentinel lymph node sites were: inguinal 172 cases (53.4%), axillary 128 cases (39.8%), inguinal and axillary 7 cases (2.2%), axillary bilateral 9 cases (2.8%), other sites 6 cases (1.8%). One sentinel lymph node was found in 210 cases (65.2%); two sentinel lymph nodes were found in 87 cases (27%), three sentinel lymph nodes in 21 cases (6.5%) and more than 3 in 4 cases (1.3%). The total number of sentinel lymph nodes was 466. In 322 patients, melanoma micrometastasis were found in 61 cases (18.9%). Such percentage is similar to that found by others: 20.6% (Morton, 1992), 21% (Thompson, 1995), 17% (Miliotes, 1996), 18% (Riccioni, 1998). In 21/59 cases (35.6%), micrometastases were detected on frozen sections. Micrometastases were detected on paraffin embedded section in 90% of cases. Immumohistochemistry was useful to detect 10% of cases.
Although prognostic parameters of primary melanomas are not complete, because some tumors had been excised in other hospitals, the analysis of data shows that the rate of positive cases is high in nodular melanomas (42.2%) and in acral lentiginous melanomas (20%); it is low in superficial spreading melanomas (12.5%). Unclassified melanomas show a very high positivity rate (40%), probably because they are generally advanced tumors. One positive case was found in level II melanomas (1.5%); positive cases were 11.2% in level III lesions, 25.7% in level IV and 81.8% in level V. No positive cases were found in melanoma of thickness <1,00 mm; positive cases were 7.5% in melanomas between 1.01 and 1.50 mm, 27.7% in melanomas between 1.51 and 3.00 mm, 38.2% in tumors between 3.01 and 4.00 mm, and 60.7 in melanomas thicker than 4.00. Of the 152 patients with melanomas thicker than 1.50, more than 1 patient out 3 patients were positive (36.2%). In the 53 patients undergone lymphadenectomy (8 patients refused the treatment), lymphatic basins excised were 57 (4 patients had two basins involved). Eight of these 57 basins contained further metastatic lymph nodes.
When the number of malignant cell is high, there are no problems to detect the metastasis; however, when melanoma cells are few, to dectet a micrometastasis may be very difficult. Malignant cells are found frequently in the subcapsular sinus, sometimes in cortical or medullary sinuses of the lymph node. Some cells simulate melanoma cells and can create difficult problems. Histiocytes containing melanin (melanophages) or other pigments, are often seen in the subcapsular sinus; they, however, are negative for S100 protein and for HMB45; reticular dendritic cells are positive for S100 protein, but not clearly evident with ematoxylin and eosin. Nevus cells of nodal nevi (in our cases 0.6% of sentinel lymph nodes) are sometimes difficult to be distinguished from melanoma cells; they, however, are contained within the lymph node capsule, rather than in the subcapsular sinus; they are S100 potive, but HMB45 negative. Other changes, as fat metaplasia and fibrosis in the lymph node may create problems in frozen material.
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The other pages
- Home Page: Dermatopathology - C. Urso, MD
- page 1: Melanoma of the skin
- page 2: Histologic diagnosis of cutaneous melanoma
- page 3: Melanoma arising in a melanocytic nevus
- page 4: Infiltration and pseudoinfiltration
- page 5: Sweat gland carcinomas
- page 6: The sentinel lymph node in cutaneous melanoma
- page 7: Bullous cutaneous diseases
- page 8: Spitz nevus
- page 9: Prognostic factors in cutaneous melanoma
- page 10: The dysplastic nevus
- page 11: Dermatofibrosarcoma protuberans
- page 12: Melanoma in situ
- last page: Questions, comments and opinions
page 13: Merkel cell carcinoma
page 14: Basal cell carcinoma
page 15: Melanoma in paediatric age