Background In childhood acute lymphocytic leukemia (ALL), relapse is most commonly seen in the bone marrow (10–20%), followed by the central nervous system (3–8%). Isolated skin relapse is very rare in ALL. We report an 8-year-old child presented with isolated skin relapse. Case presentation An eight-year-old female patient presented with swelling on the scalp 3 months after the completion of the ALLIC-BFM 2009 chemotherapy protocol administered due to the diagnosis of precursor B-cell (pre-B) ALL. Physical examination revealed a hard, painless, hyperemic, nodule-shaped lesion measuring 2 × 1 cm on the right parietal bone. Atypical hematopoietic cells with the prominent nucleolus, narrow cytoplasm, and immunohistochemically stained with CD 10, 19, 22, 79-a, and TdT were observed in the histopathological examination of the skin lesion. There was no blast in the bone marrow aspiration smear and cerebrospinal fluid. The patient was diagnosed with aleukemic leukemia cutis (LC) and pre-B ALL, presenting as an isolated relapse. Conclusion Aleukemic LC is a very rare finding after leukemia treatment. It may present with various cutaneous lesions, such as a papule, macule, plaque, nodule, palpable purpura, and ulcerative lesions. Leukemia cutis should be considered in the differential diagnosis of skin lesions developing during or after treatment in children with leukemia.

Fibrocartilaginous dysplasia (fibrous dysplasia and massive cartilaginous differentiation or fibrochondroplasia, FCD) is a rare variant of fibrous dysplasia and a term used for cases of fibrous dysplasia with prominent cartilage tissue. A limited number of FCD cases have been reported in the literature, which can be seen in both clinical forms. A 16-year-old male patient, who had been followed for ten years with a diagnosis of polyostotic fibrous dysplasia in the left hip and cranium, presented with pain in the left leg after a fall. A subtrochanteric pathological fracture in the left femur was detected on exam, the lesion area was curetted, and osteotomy and fixation were applied. Microscopic assessment revealed a fibro-osseous lesion of benign spindle cell fibrous connective tissue with woven bone trabeculae, without osteoblastic rim or large areas of benign cartilage nodules. The final diagnosis was fibrocartilaginous dysplasia. In our literature review, 26 cases of FCD were reported so far. Age distribution of patients ranged from 4 to 53 years (mean 15.9) and the male / female ratio was 15/11 = 1.36. Eighteen cases were monostotic, and 8 were polyostotic. In cases with noted clinical and follow-up data, symptom duration ranged from 8 weeks to 18 years (mean 62.2 months), with no recurrence or malignant transformation in a mean follow-up of 21.71 (2-60) months post-treatment. In the cartilage component, there was increased cellularity, some nuclear atypia, binucleation, and myxoid degeneration. This situation simulates benign and malignant entities such as enchondroma, fibrocartilaginous mesenchymoma, well-differentiated intramedullary osteosarcoma, and chondrosarcoma with a differential diagnosis. FCD is a benign and very rare lesion with a prominent chondroid component, but may cause difficulty with differential diagnosis. Awareness of the histopathological and radiological features of FCD cases, their age range, and involvement areas provides an approach to distinguish them from lesions that may be confusing in a differential diagnosis.