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.