Discussion
The ulcerative tumors occurring in our patient with MF should not be associated with the tumor-stage of typical MF. Typical MF progresses slowly from patch-stage to tumor-stage through plaque-stage over several years, but the tumor lesions in our patient occurred suddenly and grew rapidly. Therefore, the present case is incompatible with the tumor-stage of MF.
The ulcerative tumors that occurred in our patient are compatible with MF-LCT rather than CD30+ LPDs such as PC-ALCL based on the following criteria: i) LCT develops on pre-existing MF lesions, and ii) LCT consists of CD30+ large cells, which comprise ≤75% of tumor cells, and small-sized atypical lymphocyte-like cells 15,16. Recently, several studies have distinguished between PC-ALCL and LCT as follows: i) PC-ALCL cells exhibit strong expression of CCR3 and weak expression of CXCR3, while, in contrast, ii) MF cells exhibit strong expression of CXCR3 and weak expression of CCR3 17-19. In our case, more than 25% and less than 75% of the tumor lesions located on patch-lesions consisted of small-sized atypical lymphocyte-like cells and CXCR3-positive, CCR3-negative anaplastic large cells, respectively. Based on these findings, the diagnosis of MF-LCT was confirmed.
Our case shows unique features: LCT occurred in early MF and regressed spontaneously. With regard to LCT in early MF, only two cases (to our knowledge) of CD30+ MF-LCT in the patch-stage have been described previously, with both showing favorable prognoses20,21. These cases, in combination with the case reported here, strongly suggest that CD30+ MF-LCT in early MF does not indicate poor prognosis, although MF-LCT occurring in advanced MF has been reported to relate to poor prognosis 1,6. With regard to spontaneous regression of MF-LCT, there have been only a few case reports 22,23; notably, PC-ALCL was not definitely excluded in those instances. CD30+ MF-LCT, especially in early MF, also may possess the potential for spontaneous regression like that seen for CD30+ LPDs, including LyP and PC-ALCL. The accumulation of additional such unique cases is expected to contribute to deeper understanding of MF-LCT.