The relevance of morphometry in the differential diagnosis of cutaneous T cell lymphomas.

Morphometric analysis of lymphoid cells in the skin was used to differentiate between cutaneous T cell lymphomas (CTCL), i.e. mycosis fungoides (MF) and Sézary syndrome (SS), and chronic benign skin diseases. In electronmicrographs of the skin lesions from twenty patients with CTCL (group I), fourteen patients with chronic benign skin diseases (group II) and twenty-nine patients suspected of CTCL (group III), the degree of nuclear indentation of lymphoid cells, expressed as the nuclear contour index (NCI), was measured. Analysis of the NCI histograms of the infiltrating cells of group I and group II permitted us to derive classification criteria for allocating all patients correctly with a high probability (greater than or equal to 95%) in the appropriate group. Only one case was classified with a low probability (71%). The classification criteria are based on the presence of cerebriform mononuclear cells (CMC) with highly indented nuclei (NCI greater than or equal to 11.5) and the frequency distribution of CMC in the skin infiltrates expressed as the 25th and the 70th percentiles of the NCI histograms (P25 + P70). When these criteria were tested on twenty-nine patients suspected of CTCL, twenty cases were classified as malignant, nine as benign. During the follow-up period, out of the twenty patients classified as malignant, seventeen patients appeared to have or develop MF, whereas two patients had lymphomatoid papulosis and one patient is still suspected of MF. Of the nine patients classified as benign, eight patients were proven to have benign skin diseases whereas one developed MF in the follow-up period of up to 4 years. The classification results based on morphometry proved to be more sensitive than those based on DNA cytophotometry. It is concluded that morphometric analysis of lymphoid cells in the skin is of diagnostic relevance in the differential diagnosis of CTCL.