Diffuse interstitial lung disease(DILD) is a large group of heterogeneous diseases that diffusely involve the pulmonary connective tissues, principally subpleural, interlobular and alveolar wall portions. Terminology and classification of these diseases are not uniform, and the cause and the pathogenesis are unknown in many entities. It is generally accepted that the response to therapy is related to the relative degree of cellularity and fibrosis present, therefore a histologic evaluation of the relative extent and severity of these changes is required. We reviewed 52 cases of DILD from January 1990 to May 1995 diagnosed by open lung biopsy to reappraise classification and quantitative assessment of the histopathologic features. Differential histopathologic features between usual interstitial pneumonia(UIP) and nonspecific interstitial pneumonia(NIP) were examined with a correlation of HRCT findings and clinical findings. Among 52 cases of DILD, 18 cases(34.6%) were UIP, 6 cases(11.5%) were hypersensitivity pneumonia was NIP was 5 cases(9.6%), interstitial lung diseases associated with the connective tissue diseases were 5 cases(9.6%), inorganic dusts were 4 cases(7.7%), infections were 4 cases(7.7%), durgs were 2 cases(3.8%), acute interstitial pneumonia was 1 case(1.9%), sarcoidosis was 1 case(1.9%) in order of frequency plus 6 other cases(11.5%). UIP was the most frequent DILD in this study which seemed to be a criteria bias of patient selection on open lung biopsy.
Quantitative assessment of histopathologic features was useful in the differential diagnosis of DILD and differentiation of UIP from NIP was possible based on histopathologic features and supported by HRCT. UIP disclosed a significantly high score of fibrotic changes, especially in the interstitial fibrosis, smooth muscle proliferation and honeycombing, otherwise NIP appeared relatively high score in inflammatory changes. Correlation between histopathologic scores and the clinical outcome after steroid therapy or no therapy in UIP was not evident.
The dendriform pulmonary ossification (DPO) is a rare condition of unknown origin in which branching mature bony spicules, usually containing marrow, are found within the alveolar septa. DPO manifests slow progression over many years or may remain unchanged; spontaneous regression has not been recorded. Most patients have no symptoms directly attributed to the ossification, although they may have symptoms due to the underlying fibrotic process. We experienced a case of DPO in 38 year-old-man who presented with cough and sputum for a month. The chest X-ray showed marked coarsened interstitial lung markings in both lungs, especially in the lower lobes. Open lung biopsy was done. Grossly, there were significant dendriform osseous structures.
Histologically, branching arrays of mature bone were found in the interstitium and occasionally in alveolar spaces. Some bony trabeculae contained fatty or cellular marrow.
The alveolar septa showed fibrous thickening with chronic inflammation. The transition between fibrosis and bone tissue was observed. Our case suggests that dendriform pulmonary ossification may be a rare special manifestation of chronic fibrosing interstitial inflammation of the lung. Osseous structures seem to derive from metaplastic bone formation in the vicinity of undergoing fibrous process.