KRAS is detected in 30%–50% of colorectal cancer (CRC) and BRAF mutations are found in 10% of CRC. A 62-year-old man with the long-standing smoking history presented to the emergency department with abdominal pain, weight loss and constipation. CT scan of abdomen/pelvis showed obstructive mass which was found to be colon adenocarcinoma which on further molecular analysis tested positive for KRAS, NRAS and BRAF mutations. His tumour progressed despite chemotherapy and surgery and he died within a year of diagnosis. Concomitant KRAS, NRAS and BRAF mutations are rare enough to be considered mutually exclusive but coexistent mutations appear to be a distinct molecular and clinical subset which needs new and effective treatment strategies in a setting of dismal prognosis.

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Histiocytosis is a disorder when a collection of hematopoietic-derived cells multiply without regulation but is not considered malignant. The most recent classification was laid out by the World Health Organization in 2016 dividing them into multiple groups. Rosai-Dorfman disease typifies the R group and is unique in its presentation ranging from a solitary lesion or multifocal, systemic disease. CASE PRESENTATION:A 74-year-old male of African descent with a past medical history significant for tobacco abuse presented to the emergency department with hemoptysis that started 2 days prior to presentation. Patient was seen as outpatient due to hemoptysis in the past and CT chest showed a 4.2 cm mass in the left lower lobe, no lymphadenopathy; confirmed by another CT Chest in the emergency department. PET/CT at that time showed the mass had increased 18-FDG uptake with SUV 26.4. There was very high suspicion for lung carcinoma and bronchoscopy showed a friable, bleeding, pedunculated mass occupying LLL basal segmental airway. The mass was removed using a snare and forceps and the tumor base was cauterized with argon plasma coagulation. Pathology report of the mass showed proliferation of histocytes with immunostaining positive for S100 and CD68, but negative for CD1a consistent with the diagnosis of Rosai-Dorfman disease. The patient was started on definitive radiation therapy with resolution of his symptoms.DISCUSSION: Rosai-Dorfman disease (RDD) is a rare histiocytosis that is characterized as being multisystemic. First described in 1969 by Rosai and Dorfman, this was described as self-limiting painless lymph node enlargement seen in teenagers and young adults. Our patient presented in his late 70's and was of African descent. Recent publications coming from China with 25 cases of RDD showed that extranodal presentation less common in Asians compared to white/black patients, and the mean age was 45 years old. Pulmonary involvement of RDD usually involves mediastinal lymphadenopathy which our patient did not have; the PET/CT showed the disease was limited to the mass in the left lower lobe. Differentiating RDD with this presentation from malignant lung disease, especially on a patient with significant smoking history, is challenging. Histopathology will give the diagnosis -in RDD S-100 and CD68 are the common positive markers with negative CD1a ruling out Langerhans cell histiocytosis. Treatment with radiation therapy is described for localized disease-causing symptoms, our patient has had a good response with resolution of his symptoms. CONCLUSIONS: RDD is very rare to present in lungs alone with no lymphadenopathy and this presentation is difficult to differentiate from malignancy. Diagnosis is based on tissue sampling with immunohistochemistry staining characterized by (þ) S-100 and CD68 with (-) CD1a. Radiation therapy is an effective treatment for symptomatic localized disease.