Basically an entity not reported in English language papers in many years from now. There are some controversies but it is has been slowly set aside to be included within of spectrum of erythema nodosum (EN). Here are a few words of what the experts say about this pathology in a review of EN in Dermatology Online of 2002.
The term subacute nodular migratory panniculitis was coined by Vilanova and Piñol in 1956 for a variant of septal panniculitis which they considered to be clinical and histopathologically different from erythema nodosum. Fine and Meltzer favored the name chronic erythema nodosum as the best denomination for lesions previously described as erythema nodosum migrans or subacute nodular migratory panniculitis. However, more recently, some authors still believe that erythema nodosum migrans and chronic erythema nodosum are two different clinico-pathological entities. Histopathologically, lesions of erythema nodosum migrans showed marked thickening of the septa of subcutaneous fat, with an abundant number of granulomas containing frequent multinucleated giant cells, granulation tissue and conspicuous proliferations of capillaries at the separation between septa and fat lobules. In lesions of erythema nodosum migrans there was no evidence of phlebitis. In contrast, lesions interpreted as chronic erythema nodosum showed a lesser degree of thickening of the septa and less inflammatory infiltrate, but phlebitis and extravasated erythrocytes were prominent and characteristic findings. At the present moment, most authors believe that erythema nodosum migrans, subacute nodular migratory panniculitis, and chronic erythema nodosum are clinical variants which may all be included within the spectrum of erythema nodosum.
Requena L., Requena C. Erythema Nodosum. Dermatology Online Journal 8 (1):4